Several weeks ago in physics, we were discussing circular motion. At one point during the day, the class was discussing what the path of an object should be immediately after the forces causing the circular motion cease (e.g., after a string breaks). The answer that students were supposed to settle on was that the object moves in a straight path tangent to the circle–an answer that is consistent with Newton’s 1st Law. One student, however, wasn’t buying it. He thought that if you spin something fast enough you should be make it keep curving around, even after the forces have lost contact. I said, “I’m with you man. Science is all about skepticism and gathering compelling evidence and arguments. You have skepticism, now go find some compelling evidence and convince me”

Weeks later that student comes back with a coat hanger, and starts spinning the coat hanger around his finger. He says this, “If the path of my finger at the end of the coat hanger goes straight at the end of the hook, then I couldn’t possibly twirl this coat hanger around my finger. He points out specifically that it only works when he spins the coat hanger really fast-fast enough to make it all keep curving around the gap.”

Two questions:

What’s the physics here?

What’s your next move with the student?